ESoCC: Create migration command to create ChannelVersion models for old channels

[AlexVelezLl]

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Overview

As we will try to make the ChannelVersion more of a standard for querying channel version information in the future, we will need to migrate all the data that we already have stored in the channel.published_data field to ChannelVersion instances, and set the propper channel.version_info object, so that we make sure that all published channels have a channel.version_info object set.

For this:

• Query all version>0 Channels (note that we are not using the published field to support deleted channels).
• Iterate through the channels using the .iterator() method to prevent loading all channels at once. For each channel:
  • Create a ChannelVersion instance for each version present in its published_data field. Use the data set in this object to populate the information in the ChannelVersion instance. If, for some reason, published_data is null, then manually create a ChannelVersion only for the current channel version.
  • Only for the current version of the channel:
    • Set the created ChannelVersion instance as the channel version_info field.
    • If any of the following fields are missing: included_licenses, included_categories, included_languages, non_distributable_licenses_included, or special_permissions_included, then:
      • Load the content database of that channel
      • Compute all these properties. Try to reuse as much code as possible from the current fill_published_fields method.
      • When creating the AuditedSpecialPermissionsLicense objects, if the channel is public, then set the distributable field to true.

Acceptance criteria

• All channels with a version > 0 should have their version_info field set.
• All published_data versions of all channels are now available in ChannelVersion instances.